This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR99/01911 filed on Aug. 2, 1999.
The field of the invention is that of the initiating of the polymerization and/or crosslinking reactions of monomers, oligomers and/or polymers comprising reactive functional radicals capable of forming intrachain and interchain bridgings, so as to obtain a polymerized and/or crosslinked coating or composite material having a certain hardness and a certain mechanical strength.
More specifically, a subject matter of the present invention is a novel process for polymerization and/or crosslinking in the presence of novel initiators, which can be activated under an electron beam and/or gamma radiation, comprising at least one boron derivative which make possible the initiation and the progression of reactions for the formations of polymers and/or resins from substrates formed of monomers, oligomers and/or of polymers with reactive organofunctional groups.
The reactions more particularly concerned are those in which agents act as direct promoters of interchain and/or intrachain bonds. In the present case, these reactions are initiated with activation by an electron beam or by gamma radiation.
In the present description, the polymers and/or resins obtained are prepared from monomers, oligomers and/or polymers which are either (1) of organic nature, in particular solely of hydrocarbonaceous nature, or (2) of polyorganosiloxane nature and which comprise, in their structure, organofunctional groups, for example of epoxide, oxetane and/or alkenyl ether type, which react after activation by an electron beam and/or gamma radiation of the initiators according to the invention described below. In addition, it is also possible to use (3) monomers, oligomers and/or polymers with acrylic groups and/or methacrylic groups, which can be added to the polymerization medium comprising entities (1) and/or (2).
Another subject matter of the present invention is compositions comprising the polymerizable and/or crosslinkable base materials (monomers, oligomers and/or polymers), preferably of polyorganosiloxane nature, the initiators described below and, optionally, one or more additives chosen from those generally known in the applications for which these compositions are intended.
For example, these compositions can be used for the preparation of coatings on items such as solid articles or substrates, in particular a paper substrate, a fabric, a polymer film of polyester or polyolefin type, an aluminum substrate and/or a tinplate substrate.
Initiators for polymerizing and/or crosslinking monomers, oligomers and/or polymers comprising reactive organofunctional groups in their structures are disclosed in EP-0 562 897. The initiating salts of this patent represent a significant technical advance in comparison with the previously known initiators of onium salt or organometallic complex type and in particular in comparison with those in which the anion of the initiating salt is SbF6xe2x88x92, which is one of the only ones which is correct with regard to performance, but which presents serious operating problems because of the presence of heavy metals.
To assess the performances of initiators which can be activated under an electron beam and/or gamma radiation, their ability to polymerize a polymer or matrix is evaluated via tests, such as that of touch, or trade tests, such as that of the peel strength for nonstick coatings.
One of the essential objectives of the present invention is the development of a novel process which makes possible the polymerization and/or crosslinking of a matrix based on monomers, oligomers and/or polymers in the presence of novel initiators which can be activated by an electron beam and/or gamma radiation.
It should be noted that the initiators of this novel process have a markedly improved reactivity, in particular in comparison with those comprising an iodonium cation and/or antimony-derived anion within their structure. In addition, the use of these novel initiators does not necessarily require inert atmosphere conditions and, furthermore, they prove to be much less toxic.
An essential objective of the invention is to provide a high-performance process with respect to the greatest number of organofunctional monomers, oligomers and/or polymers which can be polymerized and/or crosslinked under activation with an electron beam and/or gamma radiation, the monomers, oligomers and/or polymers being in particular (1) of organic nature, preferably solely of hydrocarbonaceous nature, or (2) of polyorganosiloxane nature, optionally as a mixture (3) with other monomers, oligomers and/or polymers comprising acrylic and/or methacrylic groups.
Another essential objective of the invention is to provide a process which uses efficient initiators at a low concentration and which only requires small amounts of energy (expressed in kilograys) for carrying out the polymerization and/or crosslinking. For this reason, the industrial processes using initiators of these types prove to be particularly economical.
Another essential objective of the invention is to provide a high performance process in which the polymerization and/or crosslinking reactions are carried out at high rates. Thus, the duration of activation under an electron beam and/or gamma radiation is very short and is generally approximately less than one second and of the order of a few tenths of a second for the preparation of very thin coatings. Of course, the polymerisation/crosslinking time may vary according to the number of electron beam and/or gamma radiation sources, the duration of the activation and the distance between the composition and the activating beam(s). Thus, the process according to the invention can be employed with industrial devices in which the rate of forward progression of the composition to be crosslinked on a backing strip is very high.
Another objective of the invention is to provide compositions comprising organofunctional monomers, oligomers and/or polymers which can be crosslinked via initiators which can be activated by an electron beam and/or gamma radiation. The optimum performances are obtained in particular with compositions comprising organofunctional monomers, oligomers and/or polymers of polyorganosiloxane nature.
Another objective of the invention is to provide compositions of this type which can be used just as easily in a thin layer, the thickness of which lies, for example, in the range from 0.1 to 10 xcexcm, as in a thicker layer, the thickness of which lies, for example, in the range from a value of greater than 10 micrometers to several centimeters.
Another objective of the invention is to provide compositions of this type for the preparation of composite materials.
These various objectives are achieved by the invention, which relates first of all, in its first subject matter, to a novel process for crosslinking and/or polymerizing, under an electron beam and/or gamma radiation, compositions based on monomers, oligomers and/or polymers comprising organofunctional groups, in which process the crosslinking and/or polymerization is carried out in the presence of an initiator which can be activated by an electron beam and/or gamma radiation comprising a boron derivative of formula M+ B(Ar)4xe2x88x92 (I) where:
M+, an entity carrying a positive charge, is chosen from an alkali metal from columns IA and IIA of the Periodic Classification (CAS version),
Ar is an aromatic derivative, optionally substituted by at least one substituent chosen from a fluorine radical, a chlorine radical or a linear or branched alkyl chain, which can itself be substituted by at least one electron-withdrawing group, such as CnF2n+1, with n being between 1 and 18 (for example: CF3, C3F7, C2F5 or C8F17), F and OCF3.
According to an alternative form of the invention, M is chosen from lithium, sodium, cesium and/or potassium.
By way of example, the boron derivative of the initiator according to the invention is of formula:
LiB(C6F5)4, KB(C6F5)4, KB(C6H3(CF3)2)4 and CsB(C6F5)4.
The initiators according to the invention can be employed, as they are obtained on conclusion of their preparation process, for example in the solid or liquid form, or in solution in at least one appropriate solvent, in monomer, oligomer and/or polymer compositions which are intended to be polymerized and/or crosslinked. In the context of the invention, the term xe2x80x9csolventxe2x80x9d encompasses the products which dissolve the solid initiators and the products which dilute the liquid or solid initiators.
Preferably, the initiators are generally employed in solution in a solvent. The proportions by weight of the initiator or initiators, on the one hand, to the solvent, on the other hand, are between 0.1 and 99 parts per 100 parts of solvent and preferably from 10 to 50 parts.
The solution is subsequently used to prepare a bath with the monomer(s), oligomer(s) and/or polymer(s) comprising crosslinkable functional groups, such that the concentration of the initiator or initiators present is between 0.01 and 5% by weight in said bath and preferably between 0.05 and 0.5%.
The solvents which can be used for the initiators are very numerous and highly varied and are chosen according to the initiator used and the other constituents of the composition of the invention. In general, the solvents can be alcohols, esters, ethers, ketones and/or silicones.
The silicones used to dilute and/or dissolve the initiators can be similar or identical to the monomers, oligomers and/or polymers constituting the crosslinkable and/or polymerizable composition.
The alcohols commonly employed are para-tolyl-ethanol, isopropylbenzyl alcohol, benzyl alcohol, methanol, ethanol, propanol, isopropanol and butanol. The ethers commonly used are 2-methoxyethanol, 2-ethoxyethanol and diethylene glycol. The usual esters are dibutyl maleate, dimethyl ethylmalonate, methyl salycilate, dioctyl adipate, butyl tartrate, ethyl lactate, n-butyl lactate and isopropyl lactate. Other solvents which can be used for the bath of the initiator coming within the other categories of solvents mentioned above are acetonitrile, benzonitrile, acetone, cyclohexanone and tetrahydrofuran.
In addition, among the solvents which can be used for dissolving the initiator or initiators, some types of proton-donating organic solvents and some types of hydroxylated carboxylic acid esters have the properties also of significantly improving their performance with respect to reactivity and kinetics.
Mention will be made, among these types of solvents, referred to as reactive diluents, of:
(1) benzyl alcohol of following general formula (II): 
xe2x80x83in which:
the R0 groups are identical or different and represent an electron-donating or electron-withdrawing group chosen from linear or branched alkyls comprising 1 to 12 carbon atoms, linear or branched alkoxyls comprising 1 to 12 carbon atoms, cycloalkyls, cycloalkoxyls or optionally substituted aryls, preferably substituted by halogens or radicals such as, for example, NO2,
x is an integer between 0 and 5.
(2) hydroxylated carboxylic acid esters which are liquid at ambient temperature (23xc2x0 C.), of general formula: 
xe2x80x83in which:
the R4xe2x80x2 and R5xe2x80x2 symbols are identical or different and represent:
a linear or branched C1-C10 alkyl radical, optionally substituted by a linear or branched C1-C4 alkoxy group,
a C4-C10 cycloalkyl radical, optionally substituted by one or more linear or branched C1-C4 alkyl or alkoxy group(s),
a C5-C12 aryl radical, optionally substituted by one or more linear or branched C1-C4 alkyl or alkoxy group(s), and/or
an aralkyl or aroxyalkyl radical where the aryl part is a C5-C12 group optionally substituted by one or more linear or branched C1-C4 alkyl or alkoxy group(s) and the alkyl part is a linear or branched C1-C4 group,
it being additionally possible for the R4xe2x80x2 symbol to represent:
a linear or branched C1-C15 alkoxy radical, and/or
a C4-C10 cycloalkyloxy radical, optionally substituted by one or more linear or branched C1-C4 alkyl or alkoxy group(s).
According to a first other advantageous provision of the invention taken in its first subject matter, the polymerizable and/or crosslinkable composition is based on monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and/or of organic nature, in particular of hydrocarbonaceous nature.
According to a second other advantageous provision of the invention taken in its first subject matter, the polymerizable and/or crosslinkable composition is based on monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and/or of organic nature, in particular of hydrocarbonaceous nature, and additionally comprises monomers, oligomers and/or polymers comprising organofunctional groups of acrylate kind and in particular epoxidized acrylates, polyester glycerol acrylates, multifunctional acrylates, urethane acrylates, polyether acrylates, polyester acrylates, unsaturated polyesters or acrylic acrylates.
These acrylic entities, optionally as a mixture, which can be used with monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and/or of organic nature, are preferably chosen from the following entities: trimethylolpropane triacrylate, tripropylene glycol diacrylate, glycidylpropyl triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane ethoxylate triacrylate, bisphenol A ethoxylate diacrylate, tripropylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyether acrylates, polyester acrylates (for example the product EBECRYL 810 from UCB-Radcure) and epoxy acrylates (for example, the product EBECRYL 600 from UCB-Radcure).
According to another of the aspects of the present invention, the invention relates, in its second subject matter, to compositions comprising at least one matrix based on monomer(s), on oligomer(s) and/or on polymer(s) of polyorganosiloxine nature comprising polymerization and/or crosslinking organofunctional groups and an effective amount of at least one initiator of the type of those in accordance with the invention described above, optionally a polymerization and/or crosslinking accelerator and, optionally again, one or more additives chosen from those generally known in the applications for which these compositions are intended.
The term xe2x80x9ceffective amount of initiatorxe2x80x9d is understood to mean, in accordance with the invention, the amount sufficient to initiate the polymerization and/or the crosslinking. This amount is generally between 0.01 and 1 parts by weight, generally between 0.05 and 0.5 parts by weight, for polymerizing and/or crosslinking 100 parts by weight of the matrix.
According to a third advantageous provision of the invention taken in its first subject matter and a first advantageous provision of the invention-taken in its second subject matter, the monomer(s) and/or oligomer(s) and/or polymer(s) are of polyorganosiloxane nature, are composed of units of formula (IV) and are terminated by units of formula (V) or are cyclic and are composed of units of formula (IV) represented below: 
in which:
the R1 symbols are alike or different and represent:
a linear or branched alkyl radical comprising 1 to 8 carbon atoms which is optionally substituted by at least one halogen, preferably fluorine, the alkyl radicals preferably being methyl, ethyl, propyl, octyl and 3,3,3-trifluoropropyl,
an optionally substituted cycloalkyl radical comprising between 5 and 8 cyclic carbon atoms,
an aryl radical comprising between 6 and 12 carbon atoms which can be substituted, preferably phenyl or dichlorophenyl,
an aralkyl part having an alkyl part comprising between 5 and 14 carbon atoms and an aryl part comprising between 6 and 12 carbon atoms, which is optionally substituted on the aryl part by halogens, alkyls and/or alkoxyls comprising 1 to 3 carbon atoms,
the Yxe2x80x2 symbols are alike or different and represent:
the R1 group,
a hydrogen radical,
and/or a crosslinkable organofunctional group, preferably an epoxyfunctional and/or vinyloxyfunctional group, connected to the silicon of the polyorganosiloxane via a divalent radical comprising from 2 to 20 carbon atoms which can comprise at least one heteroatom, preferably oxygen,
and at least one of the Yxe2x80x2 symbols representing a crosslinkable functional organic group.
According to an advantageous alternative form of the invention, the polyorganosiloxanes used comprise from 1 to 10 organofunctional groups per macromolecular chain. For an epoxyfunctional group, this corresponds to epoxide levels varying from 20 to 2 000 molar meq./100 g of polyorganosiloxane.
The linear polyorganosiloxanes can be oils with a dynamic viscosity at 25xc2x0 C. of the order of 10 to 10 000 mPaxc2x7s at 25xc2x0 C., generally of the order of 50 to 5 000 mPaxc2x7s at 25xc2x0 C. and more preferably still of 100 to 600 mPaxc2x7s at 25xc2x0 C. or gums exhibiting a molecular mass of the order of 1 000 000.
When they are cyclic polyorganosiloxanes, the latter are composed of units (IV) which can be, for example, of the dialkylsiloxy or alkylarylsiloxy type. These cyclic polyorganosiloxanes exhibit a viscosity of the order of 1 to 5 000 mPaxc2x7s.
Mention may be made, as examples of divalent radicals connecting an organofunctional group of the epoxy type, of those included in the following formulae: 
As regards the organofunctional groups of the alkenyl ether type, mention may be made of those present in the following formulae:
xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CHxe2x95x90CH2, xe2x80x94(CH2)3xe2x80x94Oxe2x80x94R2xe2x80x94Oxe2x80x94CHxe2x95x90CH2 or xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CHxe2x95x90CHxe2x80x94R3
in which
R2 represents:
an optionally substituted linear or branched C1-C12 alkylene radical,
or a C5-C12 arylene radical, preferably a phenylene radical, which is optionally substituted, preferably by one to three C1-C6 alkyl groups,
R3 represents a linear or branched C1-C6 alkyl radical.
The dynamic viscosity at 25xc2x0 C. of all the silicones considered in the present description can be measured using a Brookfield viscometer according to the AFNOR Standard NFT 76 102 of February 1972.
According to a second other advantageous provision of the invention taken in its second subject matter, the matrix of the polymerizable and/or crosslinkable composition is based on monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and of organic nature, in particular of hydrocarbonaceous nature.
According to a third other advantageous provision of the invention taken in its second subject matter, the matrix of the polymerizable and/or crosslinkable composition is based on monomer(s), and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and optionally of organic nature, in particular of hydrocarbonaceous nature, and additionally comprises monomers, oligomers and/or polymers comprising organofunctional groups of acrylate kind and in particular epoxidized acrylates, polyester glycerol acrylates, multifunctional acrylates, urethane acrylates, polyether acrylates, polyester acrylates, unsaturated polyesters or acrylic acrylates.
These acrylic entities, optionally as a mixture, which can be used with monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and/or of organic nature, are preferably chosen from the following entities: trimethylolpropane triacrylate, tripropylene glycol diacrylate, glycidylpropyl triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane ethoxylate triacrylate, bisphenol A ethoxylate diacrylate, tripropylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyether acrylates, polyester acrylates (for example the product Ebecryl 810 from UCB-Radcure) and epoxy acrylates (for example, the product Ebecryl 600 from UCB-Radcure).
It should be remembered that, in the present description, the expression xe2x80x9cacrylicxe2x80x9d encompasses compounds comprising the functional group of CH2xe2x95x90CHxe2x80x94COOxe2x80x94 type or of CH2xe2x95x90C(CH3)xe2x80x94COOxe2x80x94 type.
Conventionally, the compositions according to the invention can additionally comprise one or more additives chosen according to the final application targeted.
When the polymerizable and/or crosslinkable composition is based on at least one organic entity, as a mixture optionally with monomers, oligomers and/or polymers of acrylic nature, the additives can in particular be compounds, optionally in the form of polymers, comprising mobile hydrogens, such as alcohols, glycols and polyols, of use in improving the flexibility of the cured material after polymerization and/or crosslinking; mention may be made, for example, of polycaprolactonepolyols, in particular the polymer obtained from 2-ethyl-2-(hydroxymethyl)-1,3-propanediol and 2-oxepanone, such as the product Tone Polyol-301 sold by Union Carbide or the other commercial polymers Tone Polyol 201 and Tone Polyol 12703 from Union Carbide. In addition, in this case, mention may be made, as additives, of diacids with a long alkyl chain, fatty esters of unsaturated acids which may or may not be epoxidized, for example epoxidized soybean oil or epoxidized linseed oil, the epoxidized 2-ethylhexyl ester, 2-ethylhexyl epoxystearate or octyl epoxystearate, epoxidized acrylic esters, epoxidized acrylates of soybean oil, epoxidized acrylates of linseed oil, polypropylene glycol diglycidyl ether, aliphatic epoxides with a long chain, and the like.
They can also be, whatever the nature of the polymerizable matrix, for example: fillers, such as in particular milled synthetic (polymer) or natural fibers, calcium carbonate, talc, clay, titanium dioxide, or precipitated or fumed silica; soluble dyes; oxidation and corrosion inhibitors; organosilicon or non-organosilicon adhesion modulators; fungicidal, bactericidal or antimicrobial agents; and/or any other material which does not interfere with the activity of the initiator.
For the use of the initiators according to the invention, various sources of irradiation by electron bombardment can be used to carry out the polymerization and/or crosslinking of the monomers, oligomers and/or polymers. It should be noted that the reaction mechanisms involved are of different types, one of the type identified involving cationic entities.
Mention will be made, as examples of devices which can be used, of those of pulsed electron beam type (Scanned Electron Beam Accelerator) and those of electron curtain beam type (Electron Curtain Accelerator). A pulsed electron beam device is used in the following examples and tests. By way of an alternative, gamma radiation can be used as irradiation source for the polymerization and/or crosslinking.
The resins obtained from the process or composition according to the invention can be used for the manufacture of a coating and/or composite materials. By way of nonlimiting examples, the coating prepared can be a varnish, an adhesive coating, a nonstick coating and/or an ink.